The present invention is described in its preferred embodiment as an improvement of Gibel U.S. Pat. No. 3,380,553 issued Apr. 30, 1968 ('553 patent). In this device, the dissipation of exhaust noise takes place in a silencing chamber defined in part by a porous or perforated cylinder wall through which the air is dispersed radially relatively free of noise. While the effectiveness of this air exhaust muffler has been thoroughly established in many plants around the world as an effective control of air exhaust noise from air cylinders, valves, tools, hoists, clutches, and other operating devices, there are certain maintenance requirements which must be met in order for the air exhaust muffler to maintain its designed operating parameters. In addition there are certain operating conditions in which the air exhaust muffler will not operate for its full designed service life. As an example of the former, the porous material or the disseminator must be replaced at periodic intervals, something that can be omitted or overlooked by maintenance personnel, especially when the air muffler is used with an overhead hoist or is in an otherwise inaccessible, unviewable position. As an example of the latter, even in closed loop air systems, contaminants will build up within the air lines, contaminants which can in a very short period plug up the disseminator, this even though the disseminator is otherwise no where near the end of its operating service life measured purely by hours in service. In addition certain operating conditions, such as coal mines and cotton mills, present unusual hazards for the air muffler design. These unusual conditions can result in increased back pressure for the air exhaust muffler, extremely short life, and occasionally the physical destruction of the disseminator due to a physical blow out.
This invention can also be utilized with other mufflers.